In a mass spectrometry apparatus, a mass analyzer which separates ions originating from a sample according to mass-charge ratio and a detector which detects the ions are disposed inside an analytical chamber evacuated to a vacuum by means of a high performance vacuum pump such as a turbomolecular pump. Generally, performing analysis in a state where the degree of vacuum inside the analytical chamber is not sufficiently high not only does not allow the analysis to be performed with sufficient sensitivity and precision, but also leads to contamination of the mass analyzer, detector and the like. Thus, in a conventional mass spectrometry apparatus, a vacuum gauge such as an ion gauge which monitors the degree of vacuum is additionally provided in the analytical chamber, and the monitored value for the degree of vacuum (pressure) provided by this vacuum gauge is displayed on an indicator (see Patent Literature 1, etc.). When analysis is to be performed, the analyst can check the displayed value, and if the gas pressure is higher than a certain threshold value, the analyst can judge that the vacuum evacuation is still inadequate and not perform the analysis. Furthermore, in the mass spectrometry apparatus described in Patent Literature 1, control is implemented to provide abnormality annunciation to alert the analyst in case the degree of vacuum drops during analysis.
Furthermore, in a mass spectrometry apparatus using an ambient pressure ion source, such as an electrospray ion source, a multistage differential evacuation system is employed, in which one or multiple intermediate vacuum chambers are arranged between the ionization chamber, which has a near-ambient pressure atmosphere, and the analytical chamber, which has a high vacuum atmosphere. In this sort of mass spectrometry apparatus, a vacuum gauge, such as a Pirani gauge, is provided not just in the analytical chamber but also in the intermediate vacuum chamber, which is evacuated to a vacuum by means of a rotary pump, for example, and has a relatively low degree of vacuum, and the monitored value for the degree of vacuum in the intermediate vacuum chamber is also displayed on the indicator. Therefore, the analyst is able to check the degree of vacuum not just in the analytical chamber but also in the intermediate vacuum chamber, and perform analysis in a state where an adequate degree of vacuum has been secured.
A conventional mass spectrometry apparatus as described above has a function which allows one to avoid performing inappropriate analysis in a state where the degree of vacuum is lower than the target state by monitoring the degree of vacuum in the intermediate vacuum chamber and analytical chamber. However, there are cases where the expected signal strength cannot be obtained and the analytical sensitivity and precision are low even though the degree of vacuum of the intermediate vacuum chamber and analytical chamber is adequately high. Of course, while there are various causes for being unable to obtain adequate signal strength in a mass spectrometry apparatus, the cause may involve the following problems with the apparatus.
(1) In an ambient pressure ionization mass spectrometry apparatus using a multistage differential evacuation system, in order to ensure the degree of vacuum in chambers with a higher degree of vacuum, a configuration is used wherein ions are transported to the next stage through an ion inlet unit (heated capillary, skimmer, etc.) with a very small diameter. Liquid drops caused by inadequate gasification of solvent may fly into the ion inlet unit, and clogging of the ion inlet unit occurs relatively easily. If the ion inlet unit becomes clogged, it becomes impossible to transport ions to the next stage, and the signal strength of the finally detected ions decreases.
(2) In MS/MS type mass spectrometry apparatus using a collision cell for dissociating ions through collision induced dissociation (CID), if adequate supply of CID gas such as argon into the collision cell becomes impossible due to the occurrence of gas leaks in the pipeline which supplies the CID gas or abnormalities in the operation of the gas supply valve, it will become more difficult for product ions to be produced in the collision cell. In such cases, however many precursor ions are introduced into the collision cell, the signal strength of the finally detected product ions will decrease.